I obtained an IMC rating during last year, with the intention of gaining some IR experience the cheaper way. I haven't used it much, as I'm studying for ATPL, but when I come to completing my hour building, I plan to get current with IMC flying. Hopefully this will assist me when it comes to my CPL and IR.
It's best to gain instrument experience at £100/hr instead of £400/hr on a twin! ... and will increase your chances of a first time pass - that's how I look at it anyway.
In short, I'd recommend you get one.
